<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    body {
      height: 8000px;
    }
    
    a {
      color: #FFF;
    }
    
    .actGotop {
      position: fixed;
      bottom: 50px;
      right: 50px;
      width: 150px;
      height: 195px;
      display: none;
      z-index: 100;
    }
    
    .actGotop a, .actGotop a:link {
      width: 150px;
      height: 195px;
      display: inline-block;
      background: url(images/gotop.png) no-repeat;
      outline: none;
    }
    
    .actGotop a:hover {
      width: 150px;
      height: 195px;
      background: url(images/gotop.gif) no-repeat;
      outline: none;
    }
  </style>

  
</head>
<body>
<!-- 返回顶部小火箭 -->
<div class="actGotop"><a href="javascript:;" title="Top"></a></div>


<script src="../jquery-1.12.4.js"></script>
<script>
  $(function () {
    
    //当页面超出去1000px的时候，让小火箭显示出来,如果小于1000，就让小火箭隐藏
    $(window).scroll(function () {
      if($(window).scrollTop() >= 1000 ){
        $(".actGotop").stop().fadeIn(1000);
      }else {
        $(".actGotop").stop().fadeOut(1000);
      }
    });
    
    function getScroll(){
      return {
        left:window.pageYOffset || document.documentElement.scrollLeft || document.body.scrollLeft || 0,
        top:window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0
      }
    }
    
    //在外面注册
    $(".actGotop").click(function () {
      $("html,body").stop().animate({scrollTop:0},3000);
      scrollTop为0
      $(window).scrollTop(0);
    })
    
  });
</script>
</body>
</html>